Note: Descriptions are shown in the official language in which they were submitted.
WO 94/36498 - PCT/US94/05035
21 62274
DOUBLE-WALL BOTTLE AND METHOD AND APPARATUS
FOR MOLDING THE SAME
DESCRIPTION
Technical Field
This invention relates to a double-wall bottle and a method and apparatus for
molding such a double-wall bottle.
More specifically, this invention relates to a double-wall bottle consisting
of
inner and outer bottles, where the inner bottle can be deformed by pressure
reduction
and a liquid contained therein can be sucked out by pressure reduction.
Background Art
A typical conventional vessel containing a syrup or the like has a structure
in
which the syrup is discharged by a means such as a pump.
A known type of vessel of this sort is called a bag-in-box. A bag-in-box
consists
of a synthetic resin container capable of holding, for example, five gallons
of syrup and
positioned within a rectangular corrugated cardboard box. The syrup is sucked
out of
the synthetic resin container by pressure reduction, while the container is
deformed by
this pressure reduction.
However, the bag-in-box is said to have problems, as described below. One
problem concerns the way in which the bag-in-box is difficult to handle when
it is being
transported. Another problem concerns the large number of components of the
bag-in-box, such as corrugated cardboard, a resin container, resin valves, and
metal
springs, which are of so many different materials, they are difficult to
recycle. Yet
another problem is caused by the cardboard box that surrounds the synthetic
resin
container, making it impossible to check l:he amount of contents remaining in
the
container.
A configuration disclosed in U.S latent Nos. 3,945,539, 4,350,272, and
4,921,135 is such that an inner resin container having flexibility is placed
within an
outer metal container, the inner container is deformed by increasing the
pressure in the
gap between the inner and outer containers, and thus the contents of the inner
container
are extracted.
In further configurations that put thence techniques to practical use, each of
the
inner and outer containers is a resin container, the inner container is
deformed by either
reduced pressure or increased pressure, and thus the contents are extracted
from the
inner container, as disclosed in U.S Patent Nos. 4,966,543, 5,242,085, and
5,242,086
and International Publication Number WO 92/12926.
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21 827 ~
However, the containers disclosed in the above Publications require a release
layer between the inner and outer containers. The presence of such a release
layer
makes it easy for the inner container to separate fi om the outer container,
and thus
enables the inner container to deform.
Further, in the methods of molding each of the containers disclosed in the
above
Publications, after a three-layer or five layer preform is injection-molded, a
multi-layer
container is formed by blow-molding from this multi-layer preform. Ordinarily,
if two-
layer container is molded by blow-molding from a two-layer preform in which
the
material of both the inner and outer layers is the same, the inner and outer
layers stick
together and it is not possible for the inner layer to separate from the outer
layer. With
the techniques disclosed in the above Publications, between the inner layer
and the outer
layer is provided with a release layer of a different material from that of
inner and outer
layers, in order to make it easy for the inner layer to separate from the
outer layer in a
mufti-layer container formed from a mufti-layer preform by blow-molding.
Further, if the above described mufti-layer container is formed of three or
more
layers, the two or more outer layers in intimate contact with the innermost
layer must be
formed to have air vent holes that do not pierce this innermost layer, in
order to allow at
least the innermost layer to deform by reduced pressure. Techniques for
forming these
holes are disclosed in U.S Patent No. 4,966,543 and International Publication
Number
WO 92/ 12926, but it is extremely difficult to form holes in only the outer
layers,
without touching and damaging the very thin innermost layer.
On the other hand, techniques of forming an inner container which can be
deformed by pressure reduction without the inner layer separating from the
outer layer,
and which is not provided with a release layer between the inner and outer
layers, are
disclosed in Japanese Laid-Open Patent Application Nos. 5-31791 and 58-187319.
In the method disclosed in Japanese Laid-Open Patent Application No. 5-31791,
the outer bottle is molded first by biaxial stretch blow molding, a preform
for the inner
bottle is placed in the outer bottle, and then the inner bottle is brought
into intimate
contact with the outer bottle by blowing pressurized gas into the inner
bottle. In the
method disclosed in Japanese Laid-Open Patent Application No. 58-187319, a
preform
for the inner bottle, which is of a different material and has a different
optimal
expansion ratio from a preform for the outer bottle, is placed in the outside
preform, and
then gas is blown into the inside preform to expand these two preforms
simultaneously.
With such a synthetic resin bottle, there is a desire for a double-wall bottle
which
is transparent so that the remaining amount of the contents can be observed
from the
outside. In manufacturing the double-wall bottle according to the foregoing
methods,
the problems described below have 'been encountered.
WO 94/26498 PCT/US94/05035
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In the method disclosed in the first-named Application, when the preform for
the
inner bottle is expanded, air inside this preform is expelled through a local
air expulsion
groove situated near the lip portion of the preform and communicating with the
outside
air. Therefore there is a danger that this expulsion will not be in time if
the inside
preforin is expanded instantaneously. Specifically, although the air remaining
at the
bottom of the outer bottle would have to b~e expelled out of the air expulsion
groove
immediately to match the instantaneous expansion of the preform, it is
difficult to force
air to flow toward the air expulsion groove so rapidly in the initial stages
of the
expansion, partly because of fluid resistance in space. Further, in the
initial stages
of the expansion, the inside preform comes into contact with the entire inner
wall of the
outer bottle gradually, starting from the lip portion. As a result, the
expulsion path
would be blocked so that air will remain is the initial stages of the
expansion of the
preform, thus obstructing the expulsion. Thus, if smooth expulsion is not done
to match
the instantaneous expansion of the inside preform, the stretch resistance of
the preform
would increase, which would cause incorrect expansion and thus the inner
bottle will
have an incorrect wall thickness distribution.
A structure intended to overcome this problem is disclosed in the second-named
Application. In the method of the second-named Application, the outside
preform has
air vent holes. With this structure, the inside preform is molded by biaxial
stretch blow
molding together with the outside preform having the air vent holes. The air
vent holes
will also be deformed by the expansion as the preforms are expanded. Depending
on
the degree of deformation, there is a danger that the air vent holes could be
collapsed so
that they cannot function as vents. As a result, the expansion of the inner
bottle tends to
be obstructed. The air vent holes of the outside preform are formed by
providing
projections on the molding mold halves, but use of this structure means that
an sufficient
degree of strength of the bottle cannot be achieved. Namely, synthetic resin
flows
around the projections during the molding, so that weld lines are created at
positions at
which the diverted flows of synthetic resin meet. Therefore, the resulting
bottle would
be locally weak at the weld line regions, and hence might be crushed under the
pressure
imparted during the stretch blow molding. Accordingly it is possible that a
suitable
bottle can not be obtained.
Additional problems experienced with either of the foregoing conventional
methods are described below.
With the bottle in which the outer bottle has air vent holes, a relatively
thick wall,
specifically of at least 0.1 mm, is required for the inner bottle. It is
therefore difficult to
deform the inner bottle by pressure reduction as the amount of the contents is
reduced.
On the other hand, the concept of reducing the wall thickness of the inner
bottle
is disclosed in the first-named Application. However, for the above-mentioned
reason,
WO 94/26498 PCT/US94/05035
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i.e., because instantaneous expulsion cannot be done, a uniform wall thickness
distribution is difficult to ensure during the molding. Besides, if the wall
thickness is
reduced as far as possible, the bottle will tend to be whitened by stress,
thus
deteriorating the transparency.
Another problem with the conventional art concerns the molding cycle.
Specifically, in the method disclosed in the second-named Application, the
temperatures of the outer preform and the inner preform that is to be molded
integrally
therewith by biaxial stretch blow molding must be adjusted to the optimal
expansion
temperature. It is, however, difficult during the molding cycle to
simultaneously insert
both preforms, whose temperatures have been controlled to the optimal
expansion
temperatures, because the two preforms have different wall thicknesses and
resin
materials from each other. If the two preforms have different wall
thicknesses, since the
preforms have different injection times in the hot parison method and
different heating
times in the cold parison method, the insertion of one of the preforms must be
delayed.
If the two preforms have different resin materials, their respective optimal
expansion
temperatures are different. Therefore, with the hot parison method, it is
difficult to
make the two different molding cycle times coincide with each other during the
molding. With the cold parison method, although it is difficult to make
adjustments,
molding can be performed, but in this case there is a danger that the inside
and outside
preforms will be fused to each other.
Namely, if the outer walls of the preforms are heated to a high temperature,
the
outside and inside preforms will fuse to each other when they come into
contact with
each other. Consequently it will be difficult for pressure reduction to deform
the
inner bottle molded from the inside preform.
In particular, if the two preforms are inserted together for molding, the
expansion
of these preforms would make them come into contact with each other before
being
cooled. so that it is highly likely that they will fuse to each other.
Thus, if the two preforms are inserted simultaneously, the induction cost will
increase, partly because a special molding cycle would be used and partly
because the
cycle time would be longer.
Disclosure of the Invention
With the foregoing problems in view, it is an object of this invention to
provide a
double-wall bottle consisting of an outer bottle, which can be ensured to have
sufficient
strength, and an inner bottle, which can be brought into good contact with the
inner wall
surface of the outer bottle by stretch blow molding and which can be ensured
to have
flexibility so that it can be easily deformed from the contact status by
pressure
WO 94/26498 , PCT/US94/05035
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reduction, and also suitable transparency. The invention also provides a
method and
apparatus for molding such a double-wall bottle.
Another object of the invention is to provide a double-wall bottle in which
the
inner bottle can separate easily from the outer bottle so that it can deform
as the internal
pressure is reduced, as well as a method and apparatus for molding such a
double-wall
bottle.
To achieve the above described objects of this invention, a method of molding
a
double-wall bottle comprises the steps of:
biaxial stretch blow molding a first prc:form to form an outer bottle;
forming an air vent hole in a biaxially orientated region of the outer bottle;
setting a second preforrn and the outer bottle into a first blow cavity mold,
the
second preform being placed inside of the outer bottle, the second preform
having a
bottomed body portion of an outer diameter smaller than the diameter of an
opening of
the first preform; and
biaxial stretch blow molding the second preform to form an inner bottle within
the outer bottle, while expelling air from within the outer bottle via the air
vent hole.
In the method of this invention, the outer bottle is formed by molding a first
preform by biaxial stretch blow molding, then forming air vent holes in this
outer bottle.
In comparison with air vent holes formed at the preform stage, these air vent
holes are
formed with little deformation and have dimentions almost exactly as designed.
With
the outer bottle inserted in a blow cavity mold having a cavity surface
congruous with
the contours of the outer bottle, the inner bottle is molded from a second
preform by
biaxial stretch blow molding using the outer bottle. During the entire blow
molding of
the inner bottle, from beginning to end, it is possible to expel air from
between the outer
and inner bottles via the air vent holes formed in the outer bottle, so that
the inner bottle
is not subjected to any increase in expansion resistance. It is therefore
possible to
ensure an optimal wall thickness distribution of the inner bottle. Since the
air vent holes
in the body portion of the outer bottle are formed after the outer bottle is
formed by
biaxial stretch blow molding, it is possible t:o maintain the vent holes at
substantially
their designed size, even during the blow molding of the inner bottle, so that
smooth
expulsion of air can be achieved.
Further, in the method of this invention, it is possible for the inner bottle,
which
is in intimate contact with the outer bottle, to separate easily from the
outer bottle when
it is deformed by pressure reduction. In other words, during the biaxial
stretch blow
molding, the preform for the inner bottle is cooled when it comes into contact
with the
inner wall surface of the outer bottle, because cooling takes place via the
outer bottle
from the cavity mold of the mold halves in contact with the outer wall surface
of the
outer bottle. It is therefore possible to facilitate the shaping of the inner
bottle since it is
PCT/US94105035
WO 94/26498
zl6z~~ ~
hardened as heat is taken from its surface in contact with the outer bottle.
Further, even
when it comes into contact with the outer bottle which has previously cooled
and
hardened, the inner bottle does not fuse with the outer bottle, and therefore
the inner
bottle can be separated from the outer bottle without difficulty when it is
deformed by
pressure reduction. Thus the resistance encountered when the inner bottle is
deformed
by pressure reduction can be removed.
The air vent holes formed in the outer bottle of the double- wall bottle of
the
present invention, which is molded as described above, also act as air
passageways to
allow the inner bottle to deform under reduced pressure as the contents
contained in the
inner bottle are sucked out of the firmer bottle by reduced pressure.
When the method of this invention is implemented, the first blow cavity mold
is
configured of a plurality of split molds that can freely open and close with
respect to
each other, at least one of the split molds has an air expulsion groove
communicating
from a cavity surface of the split mold to an outer surface thereof, and this
air expulsion
groove can employ a structure formed in a parting surface of the split mold.
In this case,
the air expelled from within the outer bottle via the air vent holes during
the step of
biaxial stretch blow molding the inner bottle is exhausted out of the first
blow cavity
mold via the air expulsion groove.
At this point, the air vent holes could be formed in a plurality of positions
along a
longitudinal axial direction of the outer bottle and the air expulsion groove
of the split
mold could be formed such that the shape thereof on the side in the cavity
mold is of a
longitudinally extended groove extending over the length of the region in
which the
plurality of air vent holes are formed along the longitudinal axial direction
of the outer
bottle. With this configuration, during the step of biaxial stretch blow
molding the inner
bottle, the air expelled via the air vent holes formed at different positions
in the
longitudinal axial direction of the outer bottle can be exhausted to the
outside of the
mold via the longitudinally extended groove together with the air vent holes.
The method of this invention is further characterized in that,
during the step of biaxial stretch blow molding the outer bottle, a plurality
of
circumferential concave ribs are formed at a plurality of positions along the
longitudinal
axial direction of the outer bottle, in such a manner as to extend around the
entire
circumference of the outer bottle and be indented toward the interior of the
outer bottle;
during the step of forming the air vent holes, at least one of the plurality
of air
vent holes is formed within the region in which the circumferential concave
ribs are
formed in the outer bottle;
during the setting step, a part of the circumferential concave rib of the
outer
bottle are arranged to correspond to the air expulsion groove in the split
mold; and
WO 94/26498
PCT/L1S94/05035
_,7_
during the step of biaxial stretch blow molding the inner bottle, air is
exhausted
via gaps between the cavity surface of the first blow cavity mold and the
ciicumferential
concave ribs.
With this configuration, the positions of the air vent holes of the outer
bottle and
the air expulsion grooves of the first cavity mold are such that the air can
be exhausted,
even if these positions are displaced in the ci:rcumferential direction.
The air vent holes and the air expulsion grooves are connected by annular air
passageways formed between the circumferential concave ribs and the cavity
surface.
Since the outer bottle of the double-wall bottle formed by this method is
reinforced by the circumferential concave ribs, the outer bottle can be
controlled to not
deform even when the contents are sucked out by reduced pressure. Therefore,
the inner
bottle can separate easily from the outer bottle when the contents are sucked
out by
reduced pressure, without requiring any kind of release layer between the
inner and
outer bottles.
The air vent holes can be formed outaide a region in which the circumferential
concave ribs are formed in the outer bottle. In such a case, the air in the
region bounded
by upper and lower circumferential concave ribs and the preform for the inner
bottle can
be exhausted via the air vent holes during the expansion process.
Circumferential convex ribs could be formed in the cavity surface of the first
blow cavity mold at positions corresponding to the circumferential concave
ribs of the
outer bottle. With this configuration, a mating between the circumferential
concave ribs
and the circumferential convex ribs prevents deformation of the outer bottle
during the
step of biaxial stretch blow molding the inner bottle. This pulls the inner
bottle toward
the bottom portion of the outer bottle during the expansion process of the
inner bottle,
and can prevent the formation of wrinkles in the bottom portion of the outer
bottle.
With the method of this invention, a configuration can be used in which a
circumferential groove, which communicates with air expulsion grooves formed
in
a parting surface of the split molds that form the first blow cavity mold, is
forned in a
cavity surface of the split mold. With this configuration, an air expulsion
passageway
can be ensured by the circumferential groove that provides a connection
between the air
expulsion grooves and the air vent holes, even if the positions of the air
expulsion
grooves and the air vent holes are displaced. Alternatively, a configuration
can be used
in which the air vent holes are provided communicating from the cavity surface
of the
split molds that form the first blow cavity mold to the outer wail thereof.
In the method of this invention, coolant passageways are preferably formed in
the
split molds, and the inner bottle molded within the outer bottle by biaxial
stretch blow
molding is cooled by the split molds via the outer bottle.
WO 94/26498 216 2 2 "~ ~ PCTIUS94/05035
_g_
The method of this invention further provides a structure in which the first
blow
cavity mold is configured of a plurality of split molds including a bottom
mold;
the first blow cavity mold is configured of a plurality of split molds
including a
bottom mold;
the step of forming the air vent hole includes a step of fornling the air vent
hole in
a bottom portion of the outer bottle, substantially corresponding to a parting
surface of
the bottom mold; and
during the step of biaxial stretch blow molding the inner bottle, air expelled
via
the air vent hole formed in the bottom portion of the outer bottle is
exhausted via gaps
on the parting surface of the bottom mold.
In the double-wall bottle molded by the above method, the outer bottle has a
domed bottom formed so as to protrude toward the interior of the outer bottle,
with a
base portion formed around the domed bottom, and air vent holes penetrating
from an
outer wall of the outer bottle to an inner wall thereof are formed in the base
portion or in
the vicinity thereof.
During the step of forcing the air vent holes, air vent holes could be formed
in
the bottom portion and the body portion of the outer bottle, and the number
and/or total
opening area of the air vent holes formed in the bottom portion and the body
portion
could be set to be such that an opening ratio per unit area of the bottom area
is larger
than that; of the body portion. In the final stages of the step of biaxial
stretch blow
molding the inner bottle, air can easily become trapped in the bottom portion
of the
outer bottle. By forming air vent holes of a large opening ratio in the bottom
portion,
the air concentrating in the bottom portion can be efficiently exhausted and
thus the
outer bottle and the inner bottle can be brought into intimate contact, even
in the bottom
pornon.
By making the opening ratio of the bottom portion larger in the double-wall
bottle molded by the above method, it is possible to allow air to flow in
efficiently
between the i~er and outer bottles while the contents are being sucked out,
and thus the
deformation by pressure reduction of the bottom portion of the inner bottle
can be
performed efficiently right fi om the beginning. This means that virtually all
of the
contents can be sucked out of the inner bottle.
The method described below can be employed to form the air vent holes in the
outer bottle in accordance with this invention. First, during the step of
forming the air
vent holes, it is preferable to drive heated hole-piercing members forward and
backward
relative to the outer bottle to form the air vent holes. This removes the
danger of
damage such as cracking that could occur in the outer bottle while the air
vent holes are
being formed. The step of forming the air vent holes could be implemented
within a
second blow cavity mold used during the biaxial stretch blow molding of the
first
WO 94/26498
PCT/US94/05035
-9-
preform into the outer bottle. In this case, the air vent holes are formed by
hole-piercing
members protruding from a cavity surface of the second blow cavity mold. This
step of
forming the air vent holes could also be iimplemented by driving heated hole-
piercing
members forward and backward relative to the outer bottle, after the outer
bottle has
been removed from the second blow cavity mold used during the biaxial stretch
blow
molding of the first preform into the outer bottle. In that case, the outer
bottle could be
driven intermittently, with the heated hole-piercing members being driven
forward and
backward when the rotation is stopped. Tlus process makes it easy to form the
air vent
holes at a plurality of locations around the c;ircumferential direction of the
outer bottle.
The method described below could lie employed for inserting the second preform
for the inner bottle into the outer bottle. First, a step of adjusting the
temperature of the
second preform to a suitable temperature for expansion is provided before the
step of
setting the second preform in the first blow cavity mold, then the second
preform is
inserted in such a manner that the outer bottle surrounds the second preform.
In
particular, if the temperature is adjusted by a temperature conditioning pot
surrounding
the second preform, sufficient space can be reserved for the insertion by
simply
lowering the temperature conditioning pot after the temperature adjustment
step. The
second preform and the outer bottle could lbe set together in the first blow
cavity mold.
In such a case, the first blow cavity mold could be configured of a plurality
of split
molds including a bottom mold, and the outer bottle is mounted on the bottom
mold.
The double-wall bottle of this invention consists of an outer bottle having a
biaxially oriented body portion and an inner bottle positioned within the
outer bottle and
having a biaxially oriented body portion, wherein:
the body portion of the outer bottle has a wall thickness of at least 0.3 mm
and
has an air vent hole in a biaxially orientated region of the outer bottle;
the body portion of the inner bottle h;as a wall thickness of at most 0.08 mm;
and
the inner bottle is deformable by pressure reduction as a substance contained
therein is sucked out of the inner bottle.
According to this invention, since the body portion of the outer bottle has a
wall thickness of at least 0.3 mm, the outer bottle is self supporting against
any
deformation by pressure reduction when t:he contents are sucked out and it can
be
ensured to have a strength suitably resistant; to impact during
transportation. On the
other hand, since the body portion of the inner bottle has a wall thickness of
at most
0.08 mm, the inner bottle is flexible enough to deform in answer to pressure
reduction.
Further, since the body portion of the outer bottle has a plurality of air
hole vents at
positions spaced in the longitudinal axial direction, air can be expelled and
injected
smoothly when the inner bottle expands and contracts.
WO 94/26498 PCT/US94/05035
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If both the outer and inner bottles have transparent body portions, it would
be
easy to check the remaining amount of contents. It is also preferable that the
body
portion of the inner bottle should have a wall thickness of at least 0.04 mm.
It would be
difficult for such an inner bottle to become whitened due to stress during the
blow
molding, thus ensuring transparency for the inner bottle.
The body portion of the outer bottle preferably has circumferential concave
ribs
and also air vent holes in the circumferential concave ribs. When this outer
bottle is
inserted into the blow cavity mold, it is possible to define annular air
passageways
between the cavity surface and the circumferential concave ribs of the bottle
body
portion so that the air inside the outer bottle can be expelled via the air
vent holes of the
outer bottle and the air passageways.
The outer bottle preferably has a first flange at its lip portion and the
inner bottle
has a second flange at its lip portion that is engageable with the upper
surface of the first
flange. With these flanges, since the body portion of the inner bottle expands
to a
diameter larger than the diameter of the opening of the lip portion of the
outer bottle, it
is possible to prevent the inner bottle from being removed from the outer
bottle.
If the inner bottle is provided with a reinforcing rib portion in a region
below the
lip portion that has a diameter larger than the opening defined by the lip
portion of the
outer bottle, the above removal prevention means can be made more reliable.
Further, the first and second flanges could be provided with a rotation stop
means
that prevents the outer and inner bottles from moving circumferentially
relative to each
other, wherein the rotation stop means include a pair of coacting engaging
portions
situated on the first and second flanges, respectively, so as to be engageable
with each
other.
Both the outer and inner bottles are preferably made of polyethylene
terephthalate (PET) resin, which has excellent biaxial stretch blow molding
properties.
PET resin has an excellent transparency because of its uniformly oriented
crystals, and
thus is possible to construct a double--wall bottle which is also extremely
recyclable, by
making both the outer and inner bottles of PET resin.
An apparatus for molding the double-wall bottle of this invention comprises:
a means of forn~ing an outer bottle by biaxial stretch blow molding a first
preform;
a means of forming an air vent hole in a biaxially orientated region of the
outer
bottle:
a means of setting a second preform and the outer bottle into a first blow
cavity
mold, the second preform being placed inside of the outer bottle, the second
preform
having a bottomed body portion of an outer diameter smaller than the diameter
of an
opening of the first preform; and a means of forming an inner bottle within
the outer
29 62274
-11.-
bottle by biaxial stretch blow molding the second preform
while expelling the air within the outer bottle through the
air vent hole.
This apparatus can also be provided with:
a first blow mo7_ding machine that infection-molds the
first preform and forms the outer bottle by biaxial stretch
blow molding from the first preform while retaining the heat
with which the first preform is injection-molded;
a second blow molding machine that infection-molds the
second preform and farms the inner bottle by biaxial stretch
blow molding from the second preform while retaining the heat
with which the second preform is injection-molded and which is
placed within the outer bott le; ,snd
a conveyor means that supplies and conveys the outer
bottle, ejected from the first blow molding machine, to the
second blow molding machine at a timing that matches the
timing of the biaxial stretch blew molding of the inner
bottle.
In this case, the air vent hole formation means is
provided part wa alon a
y g path along which the outer bottle is
supplied and conveyed. to the second blow molding machine.
A number N (where N >_ :1) of the second blow molding
machines and a number M (where M > N) of the first blow
molding machines could be provided connected by the conveyor
means. The molding cycle time oj_ the first blow molding
machine for forming outer bottles is slower than that of the
second blow molding machine because the thickness of the first
F
28403-4
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preform is greater than that of the second preform. In such a
case, if the number of second blow molding machines is greater
than the number of first blow molding machines, the second
blow molding machines lose no time due to waiting for outer
bottles to be supplied, thus improving the production
efficiency.
In accordance with the present invention, there is
provided a method of molding a double-wall bottle, comprising
the steps of:
biaxial stretch blow molding a first preform to form an
outer bottle having body and bottom portions;
forming air vent holes in the bottom portion of said
outer bottle;
setting a second preform an~~ said outer-bottle into a
first blow cavity mold, said second preform being placed
inside of said outer bottle, said second preform having a
bottomed body portion of an outer diameter smaller than the
diameter of an opening of said first preform; and
biaxial stretch blow moldin~~ said second preform to form
an inner bottle within said outer bottle, while expelling air
from within said outer bottle via said air vent hales;
wherein said step of forming said air vent holes includes
a step of forming air' vent holes at different positions in the
longitudinal and circumferential directions of said body
portion of said outer bottle; and
wherein, during said step oi' biaxial stretch blow molding
said inner bottle, the air within said outer bottle is
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21 62274
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expelled via said air vent holes formed at said body and
bottom portions of said outer bottle.
In accordance with another aspect of the invention,
there is provided a double-wall bottle consisting only of an
outer bottle having a biaxially oriented body portion and a
bottom portion, and an inner bottle positioned within said
outer bottle, wherein:
a plurality of air vent holes are formed in said body
portion and said bottom portion of said outer bottle, and an
opening ratio of said air vent holes per unit area is set to
be larger in said bottom portion than in said body portion.
In accordance with anoi:her aspect of the invention,
there is provided an apparatus for molding a double-wall
bottle, comprising:
a means of forming an outer bottle having body and bottom
portions by biaxial stretch blow molding a first preform;
a means of forming air vent holes in said body and bottom
portions of said outer bottle in a predetermined pattern for
enabling venting through said ho7.es;
a means of setting a second preform and said outer bottle
into a first blow cavity mold) said second preform being
placed inside of said outer bott7.e, said second preform having
a body portion of an outer diameter smaller than the diameter
of an opening of said first prefo rm and having a bottom; and
a means of forming an inner bottle within said outer
bottle by biaxial stretch blow molding said second preform
while expelling the air within said outer bottle through said
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21 62274
- llc -
air vent holes wherein said first: blow cavity mold includes
means for venting the expelled air from the air vent holes
including the air vent holes formed in the predetermined
pattern.
Brief Description of the Drawinas
FIG. 1 is a front view partly in section of a
double-wall bottle embodying this invention;
FIG. 2 is an enlarged :sectional view showing a
portion A of FIG. 1;
FIG. 3A is a sectional view showing a lip portion of
the double-wall bottle of FIG. 1 and FIG. 3B is a sectional
view showing a lip portion of another embodiment;
FIG. 4 is a fragmentary exploded perspective view
showing the lip portion of FIG. 3A;
FIG. 5 is a schematic ~lllustrative view of a
dispensing system including a double-wall bottle of this
invention;
FIG. 6 is a schematic :sectional view showing the
process of biaxial stretch blow molding an outer bottle;
28403-4
WO 94/26498 ~ PCT/US94/05035
' -1:~_
FIG. 7A and FIG. 7B are front views of an outer bottle and a preform for an
inner
bottle, respectively;
FIGS. 8A, and 8B are schematic sectional views of a double-wall bottle of this
invention, in which FIG. 8A and FIG. 8B show the step of inserting the inner
bottle;
FIG. 9 is a schematic sectional view of a double-wall bottle of this
invention,
which shows the step of biaxial stretch blow molding the inner bottle;
FIG. 10 is a fragmentary perspective view showing a blow cavity mold to be
used
in the step of biaxial stretch blow molding the inner bottle;
FIG. I 1 is a fragmentary perspective view showing a modification of the blow
cavity mold of FIG. 9;
FIGs. 12 to 14 are schematic sectional views, each showing positional
relationships between a cavity surface of a blow cavity mold and
circumferential ribs
and air vent holes formed in an outer bottle;
FIG. 15 is a schematic sectional view showing the process of biaxial stretch
blow
molding an inner bottle;
FIG. 16 is a bottom view showing the outer bottle of FIG. 15;
FIG. 17 is a schematic sectional view showing a blow cavity mold having air
vent
holes;
FIG. 18 is a plan view showing the entire structure of a double-wall bottle
molding apparatus; and
FIG. 19 is a schematic illustrative viev~r of a hole-piercing mechanism.
Best Mode for Carrying Out the Invention
A double-wall bottle and a method of molding the double-wall bottle according
to
this invention will now be described with reference to the accompanying
drawings.
FIG. 1 is a sectional view showing a double-wall bottle 10 according to one
embodiment of this invention.
The double-wall bottle 10 comprises an outer bottle 12 and an inner bottle 14,
with contents 16 such as post-mix soft drink syrup within the inner bottle 14.
The
contents 16 are discharged outside by suction through a flexible hose 18
connected at
one end to a suction pump (not shown in the figure). For this purpose, the
hose 18 is
coupled to a cap 20 mounted on the lip portion of the double-wall bottle 10
and the
other end thereof extends into the contents 16.
Note that a method to extract the content 16 from within the double-wall
bottle
to outside is not limited to one that inserts the hose 18 into the bottle as
shown in
FIG. 1. A structure for extraction of the conl:ent disclosed in U.S. Patent
No. 5,242,085
is shown in FIG. 20. According to the structure, a cap 200 is attached to the
neck
portion 14A of the double wall bottle, and a coupling 210 is attached to the
cap 200.
WO 94/26498 PCT/US94/05035
-1~3-
The hose 18, which is connected to the coupling 210, does not extend to the
interior of
the double wall bottle 10. The cap 200 inclludes a plurality of holes 202 for
evacuating
the content 16 therefrom by pressure reduction. In addition, the cap 200
includes a pin
204 to actuate (open) the valve (not shown) in the coupling 210 in the manner
known in
the art as the coupling 210 is attached to the cap 200.
The configuration of a system that dispenses syrup from the double-wall bottle
will now be described with reference to FIG. 5. The hose 18 connected to the
double-wall bottle 10 is connected to a pump 34, and the pump 34 is connected
via a
syrup line 32 to a dispenser 30. The pump 34 is connected to, for example, a
C02
source 36 via a C02 line 38, and is operated by C02 gas supplied from the C02
source
36. Any known type of dispenser can be used as the dispenser 30, to which a
syrup line
32, which will be described later, and a water supply line 40 are connected.
The
dispenser 30 has a plurality of valves 42. By opening any one of these valves
42, an
operator can cause a selected beverage to be dispensed through a nozzle 44
into a cup 46
placed on a drip tray 48. Note that, in order to make it easy to replace the
double-wall
bottle 10, the above described cap 20 attached to the lip portion of the
double-wall bottle
10 can make use of a known quick-disconnect coupling.
Both the inner and outer bottles 12 and 14 are molded by biaxial stretch blow
molding using the same kind of material. In the illustrated embodiment, the
material was
polyethylene terephthalate (PET), which has, excellent expansibility and
transparency.
Since the outer bottle is molded from a preform of PET resin by biaxial
stretch
blow molding, has a transparent body portion. The body portion has a wall
thickness of
preferably at least 0.3mm, and more preferably between 0.3mm and 0.45mm, in
order to
ensure sufficient defornling strength and transparency to enable the contents
to be seen.
Likewise, since the inner bottle is molded from a prefonm of PET resin by
biaxial
stretch blow molding, it also has a transparent body portion.
The wall thickness of the body portion of the inner bottle 14 is preferably at
most
0.08mm in order to ensure flexibility to facilitate deformation due to
pressure reduction.
The inner bottle 14 can therefore be deformed by pressure reduction as the
contents are
reduced by suction.
It is more preferable if the wall thicl~;ness of the body portion of the inner
bottle
14 is at least 0.04mm in order to prevent the inner bottle 14 from whitening
due to stress
during the blow molding and to thereby ensiue sufficient transparency.
The body portion of the outer bottle 12 has a plurality of circumferential
concave
ribs 22 at positions spaced in the longitudinal axial direction. This
increases the
mechanical strength of the outer bottle 12. Therefore, since the outer bottle
12 is
reinforced by the circumferential concave cribs 22, it does not deform when
the inner
bottle 14 within it is deformed by pressure reduction, so that separation of
the outer wall
WO 94/26498 PCT/US94/05035
-14-
of the inner bottle 14 from the inner wall of the outer bottle 12 is
facilitated without
the need of a release layer on either wall. The body portion also has a
plurality of air
vent holes 24 in the regions of the circumferential concave ribs 22.
Specifically, as shown in FIG. 2, each circumferential concave rib 22 extends
around the entire circumference of the body portion of the outer bottle 12 and
is
depressed inward, and has in its bottom portion a number of the air vent holes
24 which
are spaced from one another along the circumferential concave rib 22, with
each
extending through the body portion wall.
The air vent holes 24 are formed in, for example, a blow cavity mold used in
the
biaxial stretch blow molding of the outer bottle 12. The air vent holes 24 are
therefore
free from any deformation once they are formed. This is because the biaxial
stretch
blow molding is at the final stage of the formation of the outer bottle 12,
and the body
portion is not expanded subsequently.
Each circumferential concave rib 22 formed around the circumference of the
outer bottle 12 also serves as an air passageway for directing the air which
remains
inside the outer bottle to the air expulsion portion of the blow cavity mold
when the
inner bottle 14 is molded by biaxial stretch blow molding. This status, namely
the
relationship between the blow cavity mold and the circumferential concave ribs
22 when
the inner bottle 14 is molded by biaxial stretch blow is shown in FIG. 2 in
which the
dash-and-two-dot lines indicate a cavity surface 73B of the blow cavity mold.
An air
passageway 26 constituted between the circumferential concave rib 22 and the
cavity
surface 73B is thereby formed to communicate in the circumferential direction.
Therefore, the air expelled from within the outer bottle 12 will flow into the
air
passageway 26 from the air vent holes 24 and then will be exhausted to the
outside via
the air passageway formed in the parting surface of the blow cavity mold as
will be
described.
A lip portion 14A of the inner bottle 14 is integrally superposed on a lip
portion
12A of the outer bottle 12, as shown in FIG. 3A. The lip portion 14A of the
inner bottle
14 has on its outer circumferential surface a thread portion on which a cap is
to be
screwed, and also has on its base a second flange 14B. This second flange 14B
is
superposed on the upper surface of a first flange 12B formed on the lip
portion 12A of
the outer bottle 12. This means that the inner bottle 14 extends fi om the
opening of the
lip portion 14A, through which the contents are to be inserted, to the
remaining entire
part, in which the contents are to be accommodated. The contents accommodated
in
the inner bottle 14 are therefore kept from coming into contact with the outer
bottle 12
along the range from the opening of the lip portion to the bottom. If the
inner bottle 14
is molded fi om a so-called virgin material, the contents are prevented from
deteriorating
even when a recycled material is used for the outer bottle 12.
WO 94/26498 PCT/US94/05035
-15-
The second flange 14B and the body portion of the inner bottle 14 jointly
serve to
prevent the inner bottle 14 from being removed out of the outer bottle 12.
Namely, the
outer diameter (D 1 ) of the body portion extending from the lip portion 14A
of the inner
bottle 14 is larger than the diameter (D2) of the opening of the lip portion
12A of the
outer bottle 12. The outer bottle 12 and inner bottle 14 are therefore
prevented from
mutually separating because the first flange 12B of the outer bottle 12 and
the body
portion of the outer bottle 12 are sandwiched between the lower surface of the
second
flange 14B and the body portion of the inner bottle 14.
The structure shown in FIG. 3B can be used additionally as a removal
prevention
means. In FIG. 3B, a reinforcing rib or stepped portion 14C is formed as close
as
possible to the lip portion 12A of the outer bottle 12, over a region of a
diameter greater
than the diameter D2 of the opening of t:he outer bottle 12. The formation of
this
reinforcing rib 14C causes a rib 12E to be formed in the corresponding portion
of the
outer bottle 12. Since the portion of the inner bottle 14 reinforced by the
rib 14C is
difficult to deform, the inner bottle 14 is prevented from being removed from
the outer
bottle 12. Alternatively, instead of forming the rib 14C in the inner bottle
14, or to
further supplement it, a non-deformable structure could be used in which the
wall in the
region corresponding to the rib 14C is made comparatively thicker.
Further, the first and second flanges 12B and 14B ca.m~ on their confronting
surfaces a rotation stop means for preventing; the two bottles from mutually
rotating.
FIG. 4 shows the confronting surfaces of the lip portions. As shown in FIG. 4,
an
engaging hole 12B 1 is formed in the upper surface of the first flange 12B,
and an
engaging pin 14B I engageable with the engaging hole 12B 1 is integrally
formed on the
lower surface of the second flange 14B. The inner bottle 14 is preventing from
rotating
with respect to the outer bottle 12 by fitting the engaging pin 14B I on the
second flange
14B into the engaging hole 12B 1 of the first flange 12B.
The method of molding the double-wall bottle 10 of FIG. 1 will now be
described.
FIGs. 6 to 9 illustrate the molding steps.
The molding method of this invention comprises the following steps:
( 1 ) molding a preform for the outf:r bottle;
(2) controlling the temperature of the outside preform and molding it by
biaxial stretch blow molding to form the outer bottle;
(3) forming air vent holes in the outer bottle;
(4) molding another preform for tile i~er bottle;
(5) controlling the temperature of the inside preforrn and inserting the
inside
preform into the outside bottle; and
WO 94/26498 PCT/US94105035
-16-
(6) molding the inside preform by biaxial stretch blow molding to form the
inner bottle.
The individual molding steps will now be described in detail.
( 1 ) In this step, a preform 50 for the outer bottle is molded by, for
example.
injection molding. Since this step requires no special process for the
preform, it may be
carned out by an ordinary injection molding process.
(2) In this step, as shown in FIG. 6, after the outside preform 50 is conveyed
clamped by a lip mold 51 and the temperature is controlled to an optimal
expansion
temperature, the outside preform 50 is set in a blow cavity mold 52 for
molding the
outer bottle. The blow cavity mold 52 has an inwardly indented cavity surface
52 A for
molding the circumferential concave ribs 22 which are to be molded in the body
portion
of the outer bottle 12. A blow core mold 54 is inserted into the lip portion
of the outside
preform 50. Further, an stretching rod 56 passing through an air passageway
54A of the
blow core mold 54 is placed within the outside prefortn 50. Thus, the outside
prefonn
50 is expanded in the longitudinal axial direction by the stretching rod 56
and also in the
transverse axial direction by the blowing of air introduced through the blow
core mold
54, so that it is biaxially expanded. While it is thus expanded, the
circumferential
concave ribs 22 are formed in the body portion. The wall thickness of the body
portion
of the outer bottle 12, formed by the biaxial stretch blow molding, is
preferably set to be
at least 0.3mm. Therefore, sufficient deforming strength and sufficient
transparency can
be ensured for the resulting outer bottle 12.
(3) In this step, as shown in FIG. 6, the blow cavity mold 52 for biaxial
stretch blow molding is used. The blow cavity mold 52 carries needles 60 which
project
retractably from the inwardly indented cavity surface that forms the
circumferential
concave ribs 22, toward the center of the mold 28. These needles 60 are
provided to
form the air vent holes 24 in the body portion of the outer bottle 12. For
this purpose,
the needles 60 are arranged at positions spaced around the circumferential
direction of
the cavity surface corresponding with the positions at which the air vent
holes 24 are to
be formed. The needles 60 are heated so that they can pierce the body portion
easily.
The heating temperature for the needles 60 is preferably higher than the
temperature to
which the outside preform is controlled. Therefore, expanding the outside
preform 50 in
the transverse direction will bring it into contact with the cavity surface to
form the
circumferential concave ribs 22. After that, for example, the air vent holes
24 are
formed by the needles 60. Since the air vent holes 24 are formed in the final
molding
step rather than during the molding of the outside preform, the holes are
unlikely to
deform or collapse, compared with the case in which the air vent holes 24 are
formed in
the preform.
WO 94/26498 PCTIUS94/05035
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Next, an example of the drive mechanism of the needles 60 will be described,
with reference to FIG. 6. Hole-piercing means for forming the air vent holes
24 arrayed
in a line along the longitudinal axial direction of the outer bottle 12, such
as the needles
60, are each fixed to ends of a plurality of shafts 62. The other ends of the
shafts 62
extend out of the blow cavity mold 52 and are fixed to a movable plate 64.
This
movable plate 64 is linked to a rod 66A that is driven forward and backward by
an air
cylinder 66.
When the outer bottle 12 is to be formed within the blow cavity mold 52, the
movable plate 64 is retracted by the air cylinder 66. As a result, the points
of all of the
needles 60 are retracted to a position at which they do not protrude from the
cavity
surface of the blow cavity mold 52. After the outer bottle 12 has been formed
in the
blow cavity mold 52, the air cylinder 66 is driven to drive all of the needles
60 so as to
protrude from the cavity surface and thus firm the air vent holes 24 in the
body portion
of the outer bottle 12. The movable plate E.4 could also be connected to a
heater power
source 68. In such a case, heaters connected to the needles 60 are installed
within the
movable plate 64 and the shafts 62 and these heaters are heated by the power
source 68,
so that the needles 60 can be heated to a temperature at which they can easily
form the
air vent holes 24.
After the outer bottle 12 has been formed in the blow cavity mold 52 and the
air
vent holes 24 have been formed therein by the needles 60, the outer bottle 12
is taken
out of the blow cavity mold 52 by a mold opening means.
Then. as shown in FIG. 7A, the outer bottle 12 is taken out from the lip mold
51 by a non-illustrated ejection mechanism. The outer bottle 12 is then
hardened by, for
example, natural cooling.
(4) In this step, as shown in FIG. 7B, a preforrn 70 for the inner bottle 14
is
molded by injection molding in a similar manner to the outer bottle 12. The
inside
preform 70 should preferably be injection nnolded under conditions such that
the wall of
the inside preform 70 is not too thin. This prevents deterioration of the
fluidity of the
resin that flows between the confronting cavity surfaces of the injection
cavity mold and
the injection core mold. If the fluidity of the resin were to deteriorate, a
so- called short
shot phenomenon in which resin is not fully supplied over the entire cavity
surface could
occur, or it may be necessary to lengthen the cycle time until the resin is
fully supplied.
Therefore, in this embodiment, the inside preforrn 70 has a wall thickness of
about 2
mm. The length of the inside preform 70 in the longitudinal axial direction
based on
this wall thickness is set in view of the air .expulsion pressure and the
expansion rate, in
such a manner that the wall thickness after the final molding step preferably
ranges
between 0.04 mm and 0.08 mm. In this embodiment, the length of the inside
preform 70
is approximately half that of the outside preform 50. Thus the setting of the
wall
WO 94/26498 PCT/US94/05035
-18-
.
thickness is an important factor in the expansion molding, to ensure the
transparency of
the preforms.
(5) The structure of a blow cavity mold 72 to be used in the step of biaxial
stretch blow molding the inside preform 70 is shown in FIG. 10.
The blow cavity mold 72 is composed of two mold halves 72A and a bottom
mold 72B. Air expulsion grooves 74 are formed in a so-called parting surface
73A of the
mold half 72A, extending from a cavity surface 73B to an outside wall surface
73C.
These air expulsion grooves 74 can be aligned with the circumferential concave
ribs 22
formed in the body portion of the outer bottle 12. Therefore, the air
expulsion grooves
74 can communicate with the air vent holes 24 formed in the circumferential
concave
ribs 22. The blow cavity mold 72 is also provided with coolant passageways 76
for
circulating a coolant in a number of places. This will assist in cooling the
outer bottle
12 in contact with the cavity surface 73B.
The outer bottle 12 that has been naturally cooled in the atmosphere is placed
on
the bottom mold 72B of the blow cavity mold 72. The circumferential concave
ribs 22
molded in the body portion of the outer bottle 12 are therefore aligned with
the air
expulsion grooves 74 of the blow cavity mold 72. Then the inside preform 70 is
inserted into the outer bottle 12 on the bottom mold 72B from the opening of
the outer
bottle 12. At that time, as shown in FIG. 4, the second flange 14B of the
inside preform
70 is superposed on the first flange 12B of the outer bottle 12, and the
engaging pin
14B 1 on the second flange 14B is fitted into the engaging hole 12B 1 into the
first flange
12B so that the inner bottle 14 is prevented from rotating with respect to the
outer bottle
12. Alternatively, the engaging pin 14B 1 may be replaced by a key. In this
step, since
the outer bottle 12 is set on the bottom mold 72B of the blow cavity mold 72,
it is
unnecessary to hold the lip portion of the outer bottle 12. It is therefore
possible to
avoid any interference when the inside preform is inserted.
FIG. 11 shows, as an illustrative example, an alternative air expulsion
structure of
a blow cavity mold 78 which allows the outer bottle 12 to be devoid of
circumferential
ribs; the same reference numbers as those of FIG. 9 designate the same parts.
The blow cavity mold 78 to be used for this air expulsion structure is
composed
of similar mold halves as those of FIG. 9, and parting surface 73A of the blow
cavity
mold 78 has air expulsion grooves 74 extending from the cavity surface 73B to
the
outside wall surface 73C.
In the cavity surface 73B there are circumferential grooves 79, which
communicate with the air expulsion grooves 74, at positions spaced in the
longitudinal
axial direction, the circumferential grooves 79 being adapted to be aligned
with the air
vent holes 24 of the outer bottle 12. Each of the air expulsion grooves 74
may, for
WO 94/26498 PCT/US94I05035
- I 9-
example, communicate with the circumferential grooves 79 at one or more
positions
spaced in the longitudinal axial direction.
The outer bottle 12 naturally cooled in the atmosphere is placed on the bottom
mold 72B (FIG. 8A) of this blow cavity mold 78.
It is possible to ensure air expulsion passageways for this outer bottle 12 by
setting the outer bottle 12 so as to align tree air vent holes 24 with the
circumferential
grooves 79 in the cavity surface 73B, even if there are no circumferential
concave ribs
22 on the body portion.
The width and depth of each circumferential groove 79 should be such that the
pressure imposed during biaxial stretch blow molding does not cause the body
portion of
the outer bottle 12 to penetrate into the circumferential groove 79.
(6) In this step, as shown in FIG. 9, before the biaxial stretch blow molding,
the two mold halves 72A confronting the body portion of the outer bottle 12
are clamped
with respect to the outer bottle 12 placed o~n the bottom mold 72B. The inside
preform
70 is then expanded in the longitudinal axial direction by an stretching rod
80 and in the
transverse axial direction by the blowing of air from a blow core mold 82. As
the inside
preform 70 expands progressively from the lip toward the bottom, the air
remaining
inside the outer bottle 12 will be expelled via the air vent holes 24 formed
in the outer
bottle 12.
At this time, since a plurality of air vent holes 24 are formed in the body
portion
along the longitudinal axial direction of the outer bottle 12, the air can be
expelled
smoothly through at least some of the air vent holes 24 and the expansion of
the inside
preform 70 is thus not locally impeded. Note that, these air vent holes 24
need not be
formed in a single line along the longitudinal axis, provided they are formed
at different
positions in the longitudinal axial direction of the outer bottle 12. Note
also that it is
preferable to form the air vent holes 24 at different positions in the
circumferential
direction of the outer bottle 12, from the point of view of facilitating the
smooth
expulsion of air. The air expelled from the air vent holes 24 is directed to
the air
expulsion grooves 74 of the blow cavity mold 72 through the circumferential
concave
ribs 22 and then is exhausted out of the blow cavity mold 72. Thus, since
expulsion in
the direction in which the inside preform is to be expanded can be performed
reliably, it
is possible to prevent the expansion resistance of the prefonn from
increasing, thus
preventing the wall thickness distribution :From deteriorating. Even if the
air vent holes
24 of the outer bottle 12 are not aligned vvith the air expulsion grooves 74
of the blow
cavity mold 72, it is possible to direct the air which is expelled via the air
passageways
26 formed by the gaps between the circ:umferential concave ribs 22 and the
cavity
surface 73B, as shown in FIG. 2, to the air expulsion grooves 74. As a result,
smooth
expulsion can be achieved over the entire area of the inner bottle 14.
WO 94/26498 PCT/US94/05035
-20-
Since it can be expanded without external pressure, the inside preform 70
comes
into intimate contact with the inner wall surface of the outer bottle 12. The
inside
preform 70 in contact with the inner wall surface of the outer bottle 12 will
then be
molded into a shape corresponding to the contours of the inner bottle 14, at
which time
the inner wall surface of the outer bottle 12 serves as a cavity surface.
Since the firmer
bottle 14 in contact with the inner wall surface of the outer bottle 12 will
also be cooled
by the outer bottle 12, as shown in FIG. 9, the inner bottle 14 can harden
instantaneously and hence the shaping of the inner bottle can be facilitated.
The inner
bottle 14 can also be brought into intimate contact with the inner wall
surface of the
outer bottle 12, without fusing with the outer bottle 12.
An example of a variation of the cavity surface 73B of the blow cavity mold 72
is
shown in FIG. 12. Circumferential convex ribs 90 that can mate with the
indentations of
the circumferential concave ribs 22 are formed in the cavity surface 73B of
the blow
cavity mold 72 at positions corresponding to the circumferential concave ribs
22 of the
outer bottle 12. Experiments performed by the inventor of this invention have
verified
that, when the inner bottle 14 is blow-molded within the outer bottle 12, the
outer bottle
12 is pulled toward the bottom portion during the expansion process of the
inner bottle
14, and wrinkles occur close to the bottom portion. In this case, the mating
shown in
FIG. 12 between the circumferential concave ribs 22 of the outer bottle 12 and
the
circumferential convex ribs 90 protruding from the cavity surface 73 B ensures
that
deformation of the outer bottle 12 is prevented. In this case, the shape of
the cavity
surface 73 B of the blow cavity mold 72 can be made to be the same as that of
the cavity
surface of the blow cavity mold 52. Since the outer bottle 12 is constricted
during the
blow-molding of the inner bottle 14, gaps can be ensured between the
circumferential
concave ribs 22 of the outer bottle 12 and the circumferential convex ribs 90
protruding
from the cavity surface 73B. By being forced through these gaps, the air
within the
outer bottle 12 can be led out of the blow cavity mold 72 via the air
expulsion grooves
74.
A variation on the positioning of the air vent holes 24 formed in the outer
bottle
12 is shown in FIG. 13. In this embodiment, the air vent holes 24 are not
formed within
the region of the circumferential concave ribs 22; they are formed in a region
sandwiched between upper and lower circumferential concave ribs 22. In this
embodiment, if the upper and lower circumferential concave ribs 22 are
arranged
comparatively closely, the advantages listed below are obtained. That is, in
this case,
the inside preform 70 of the expansion process is in intimate contact with the
inner wall
at the upper and lower circumferential concave ribs 22, as shown in FIG. 13.
Therefore,
since the air vent holes 24 open into a region 92 bounded by the upper and
lower
circumferential concave ribs 22 and the inside preform 70, it is possible to
lead the air
WO 94126498 PCT/US94l05035
-21-
within that region 92 out to the exterior of the blow cavity mold 72. As a
result, it is
possible to reduce molding faults caused by trapped air.
An embodiment combining the embodiments of FIG. 12 and FIG. 13 is shown in
FIG. 14. Use of this embodiment makes it possible to prevent the formation of
wrinkles
in the outer bottle 12 during the blow molding of the inner bottle 14, and
allow the air
within the region 92 to be expelled smoothly. Note that if a large number of
air vent
holes 24 is to be formed in the body portion of the outer bottle 12, they can
be provided
in both the molding region of the circumferential concave ribs 22 and outside
that
region, as shown in Fig. 13.
Yet another embodiment of this invention is shown in FIG. 15. In this figure,
components that have the same functions as those in FIG. 9 are given the same
reference
numbers and detailed descriptions thereof are omitted below. With this
embodiment. an
upwardly domed bottom 12C is provided in the bottom portion of the outer
bottle 12 so
as to form a protrusion extending inward. For this purpose, a blow cavity mold
100
therefore is configured of two mold halves 102 (only one is shown in the
figure) and a
bottom mold 104 for forming the domed bottom. A parting surface 102A of the
mold
half 102 has a plurality of air expulsion grooves 103 communicating from a
cavity
surface 102B thereof to an outer surface 10:?C, in a similar manner to that
shown in FIG.
9. With this embodiment, the plurality of air expulsion grooves 103, on the
side facing
the parting surface 102A of the mold half 102, forms a longitudinal groove
103A
provided so as to extend over the region in which the plurality of air vent
holes 24 are
provided in the longitudinal axial direction of the body portion of the outer
bottle.
A large number of air vent holes 24 are also formed in the bottom portion of
the
outer bottle 12, as shown in FIG. 16. Two characteristics are obtained by
having such
air vent holes 24 in the bottom portion of the outer bottle 12 can be cited.
One characteristic is that the air vent holes 24 of the bottom portion are
provided
in the vicinity of a narrow ridged base portion 12D around the domed bottom
12C. The
reason for this is described below. In general, if the bottom portion of a
bottle has a
domed bottom shape, a narrow ridged base portion 12D is inevitably formed
corresponding to a parting surface 106 between the mold halves 102 and the
bottom
mold 104 of the blow cavity mold 100. There is a slight gap at this parting
surface 106.
Therefore, if air vent holes 24 are formed in the vicinity of the narrow
ridged base
portion 12D, it is possible to allow air to escape through the air vent holes
24 and the
gap over the parting surface 106. The air vent holes 24 could be formed in the
base
portion 12D itself. However, from considerations of the stability of the
bottle, it is
preferable that the air vent holes 24 are formed at a position away from the
base portion.
21 6227 4
-22-
The other characteristic is that the opening ratio
of the air vent holes 24 per uniiw area is set to be larger in
the bottom portion than in the body portion of the outer
bott le .
The opening ratio is dc~ffined as
n x h/S,
where "h" is the opening arE~a of one hole 24, "n" is the
number of holes in a unit area, and "S" is the unit area. As
shown in FIG. 16, for example, eight air vent holes 24 are
formed in each of two concentric circles on the outer side of
the narrow ridged base portion 12D of the bottom portion to
give a total of 16 such holes. :Ln contrast with the bottom
portion where these 16 air vent Boles 24 are concentrated in a
comparatively cramped predetermined area, the number of air
vent holes 24 provided in the same predetermined area of the
body port ion is less than that in the bottom port ion. With
the embodiment shown in FIG. 15 and FIG. 16, the opening areas
of the air vent holes 24 in the body portion and bottom
portion of the outer bottle 12 a;ce the same, but their
respective numbers are different, but the same result could be
obtained by making th.e numbers the same but the area of the
air vent holes 24 in the bottom ~~ortion bigger.
The reasons for setting the positions and opening
ratios of the air vent holes in -the bottom portion as
described above will now be cons dered below. During the step
of biaxial stretch blow molding 'the inner bottle 14, the
preform 70 for the inner bott le <~rrives at the cavity surface
28403-4
-23~- 21 6 2 2 7 4
102B of the blow cavity mold 100 from above. In the final
stages of this expansion process, the bottom portion of the
inside preform 70 comes into contact with the top of the
bottom mold 104, until it finally reaches the cavity surface
in the vicinity of the narrow ridged base portion 12D. In
other words, air is highly likel~~ to become trapped in the
bottom port ion of the outer bott l.e 12, part icularly in the
vicinity of the base portion 12D. With this embodiment, air
vent holes 24 are formed where ai.r is likely to become
trapped, so the likelihood of air becoming trapped in the
outer bottle 12 is reduced. If this likelihood of air-
t rapping is removed, the inner be>tt le 14 can come into
intimate contact with the outer bottle 12, even at the bottom
portion thereof, so that the quality of the double-wall bottle
10 can be improved and thus the Effective volume within the
inner bottle 14 that can contain the syrup can be increased.
Hy increasing the opening ratio of the air vent holes 24 in
the bottom portion end of the outer bottle 12, it becomes
possible to smoothly implement the operation of Expelling air
during the final stages of the bi.axial stretch blow molding of
the inner bottle 14. Note that air expulsion grooves could
also be formed in the parting surface 106. Additionally, air
vent holes can be formed in the bottom mold 104, so that air
vent passageway can be formed other than in the parting
surface 106.
The above embodiment i~r~plements air expulsion by
using the parting surface of the split molds or the bottom
28403-4
21 622 7 4
-23et-
mold, but it should be obvious to those skilled in the art
that this invention is not limitf~d to this air expulsion
method. In a still further embodiment shown in FIG. 17, air
vent holes 114 are formed in each of two split molds 112A and
112B that configure a blow cavity mold 110. Air expulsion
grooves 118 are formed in a parting surface 116. In this
case, the air vent holes 114 and air expulsion grooves 118 of
the split molds 112A and 112B opE~n at positions that
correspond with the air vent holE~s 24 formed in the outer
bottle 12. In other words, when the outer bottle 12 is
inserted into the blow cavity mold 110, it is necessary to
posit ion the outer bott le 12 in ;such a manner that the air
vent holes 24 around the circumference thereof are aligned
with the air vent holes 114 in the split molds 112A and 112B.
A plan view of a blow nnolding apparatus that is
suitable for implementing the method of this invention is
shown in FIG. 18. As shown in this figure, the apparatus in
accordance with this embodiment .Ls provided with a plurality
(such as two) of first blow mold~_ng apparatuses 130 for
molding outer bottles 12, for second first blow molding
apparatus 120 for molding inner bottles 14. From the two
first blow molding apparatuses 130 is provided a conveyor path
140 for supplying and conveying outer bottles 12 to the second
blow molding apparatus 120.
The first and second b7.ow molding apparatuses 130,
120 are installations that are known in the art, such as four-
station blow molding apparatuses. An infection molding
28403-4
21 62274
-23ta-
station 122 in the second blow m~alding apparatus 120 injects
and molds preforms 70. A temper,~ture conditioning station 124
adjusts the temperature of each injection molded preform 70 to
a temperature suitable for expan;aion. A blow molding station
126 blow-molds an inner bottle 1~4 out of preform 70, within
the outer bottle 12, to form a d~~uble-wall bottle. An
ejection station 128 ejects the completed double-wall bottle
from a lip mold. This double-wall bottle 10 is conveyed
out of the second blow molding a~?paratus 120 by an ejector
10 129.
Similarly, each of the two first blow molding
apparatuses 130 has an injection station 132, a temperature
conditioning station 134, a blow molding station 136, and an
ejection station 138. Each outer bottle 12 ejected by the
ejected station 138 is transferrE~d to the conveyor path 140 by
an ejector 139. The outer bottles 12 from the two first blow
molding apparatuses 130 are conveyed in series along the
conveyor path 140. During this mime, the stations of the
first blow molding apparatuses 130 could be arranged such that
the ejection stations 138 of the first blow molding
apparatuses 130 are opposite one another. This is because the
single conveyor path 140 can be used in common by the two
first blow molding apparatuses 1:30. Partway along the
conveyor path 140 is provided a hole-piercing mechanism 150
that forms the air vent holes 24 in outer bottles.
One embodiment of the dole-piercing mechanism 150
will now be described with reference to FIG. 19. As shown in
28403-4
21 62274
-23~~-
this figure, the hole-piercing mechanism 150 has a turntable
152 on which an outer bottle 12 is placed to rotate. The
turntable 152 has a
'' 28403-4
WO 94/26498 PCT/US94105035
-24-
X162274
gear 152A at its peripheral edge. This gear 152A meshes with a gear 154A that
is fixed
to an output shaft of a motor 154, to impart a rotational force to the
turntable 152. The
turntable 152 is also provided with an opening 1528.
A plurality of needles 156A for forming air vent holes 24 in the bottom
portion of
the outer bottle 12 is arranged below the turntable 152. These needles 156A
are fixed to
a movable plate 158A that is raised and lowered by an air cylinder 160A.
Similarly, a
plurality of needles 1568 are arranged to the; side of the outer bottle 12 in
order to form
air vent holes 24 in the body portion of thc: outer bottle 12. These needles
1568 are
fixed to a movable plate 1588 that is raised and lowered by an air cylinder
1608.
When it comes to forming the air vent holes 24 in the bottom portion and body
portion of the outer bottle 12 mounted on the turntable 152, first the air
cylinder 160A
operates. This raises and lowers the needles 156A through openings 152b in the
turntable 152, to form a plurality of air vent holes 24 in the bottom portion
of the outer
bottle 12. During this time, the outer bottlle 12 could be held by, for
example, a lip
portion thereof, in order to prevent the outer bottle from retreating upward.
After the
needles 156A have been driven downward, the air cylinder 1608 is driven to
make the
needles 156B form a line of a plurality of aiir vent holes 24 along the
longitudinal axial
direction of the body portion of the outer bottle 12. After these needles 1568
have been
driven backwards, the turntable 152 is intermittently rotated through a
required angle.
By driving the needles 1568 forward and backward at positions where this
rotation
stops, in the same way as described above, it is possible to form a plurality
of air
vent holes 24 arranged in both the circumfc:rential and longitudinal axial
directions in
the body portion of the outer bottle 12. Note that if the needles 156A and
1568 are
heated, as described above with reference to a previous embodiment, the hole-
piercing
can be performed smoothly.
Each of the outer bottles in which air vent holes 24 have been formed while
being
conveyed along the conveyor path 140, and a inside preform 70 that has been
heated to a
suitable temperature by the temperature conditioning station 124 of the second
blow
molding apparatus 120 is inserted by an inserter 170 so that the outer bottle
surrounds
the preform. During this time, the inside prc:form 70 and the outer bottle 12
could have
a configuration such that the outer bottle 1', 2 is prevented from falling off
the inside
preform 70. The reason why the preform is inserted into the outer bottle 12 at
the
temperature conditioning station 124 is because sufficient space can be
reserved for the
insertion by lowering a temperature conditioning pot.
The reason why two first blow molding apparatuses 130 are connected to one
second molding apparatus 120 is described below. As stated above. the outside
preforms 50 formed by injection molding in the first blow molding apparatuses
130 have
thicker walls than the inside preforms 70. Therefore, the injection molding
cycle of
WO 94/26498 PCT/US94/05035
_p5_
each first blow molding apparatus 130 for ir.~jection molding the thicker
outside preforms
50 is longer than that of the second blow molding apparatus 120. In general,
the station
that requires the longest processing time in .a four- station blow molding
apparatus is the
injection molding station, and this processing time usually determines the
molding cycle
time of the molding apparatus. Therefore, the molding cycle time of the second
blow
molding apparatus 120 is shorter than that of the first blow molding
apparatuses 130.
This means that, if outer bottles are not supplied fiom a plurality of first
blow molding
apparatuses 130, the outer bottles 12 can no longer be supplied at a timing
that matches
the blow-molding of the inner bottles 14 in l:he second blow molding apparatus
120.
In this way, a continuous supply of double-wall bottles 10 can be molded if a
number M (M >N)of first blow molding apparatuses 130 are provided for a number
N
(where N >_ 1 ) of second blow molding apparatuses 120, in accordance with the
difference in cycle time between the first and second blow molding apparatuses
130 and
120. If the cycle times of the first and second blow molding apparatuses 130
and 120 re
substantially the same, one each of the first and second blow molding
apparatuses 130
and 120 could be connected together.
Incidentally, embodiments of the present invention do not have to be the type
which have inter-connection between the outer bottle molding machine and the
inner
bottle molding machine. In other words, embodiments of the present invention
can be
made by conveying outer bottles, made and stocked beforehand, to the site
where there
is a inner bottle molding machine to mold a~n inner bottle with the inserted
outer bottle.
Note that this invention is not limited to the embodiments described above; a
variety of different embodiments thereof can be conceived within the scope of
the
present invention. For example, the contents sucked out of the double-wall
bottle 10 by
reduced pressure are not limited to syrups, they could be any liquid that can
be sucked
out by such reduced pressure.
Note also that the shape of the air vent holes 24 formed in the outer bottle
12 is
not limited to a circular hole; the air vent holes 24 could be any other
shape, such as
triangular, square, polygonal, or oval. In such a case, members corresponding
to the
shape of the holes to be formed can be used.
As described above, according to the double-wall bottle of this invention, it
is
possible to ensure sufficient transparency a~zd deforming strength. Since the
inner bottle
is expanded in a desired manner during the biaxial stretch blow molding, it is
possible to
optimize the wall thickness distribution so that a wall thickness that can
maintain
sufficient flexibility can be obtained.
According to the double-wall bottle molding method of this invention, since it
is
possible to expel the air which remains inside the outer bottle reliably when
the inner
bottle is molded by biaxial stretch blow molding, it is possible to expand the
inner bottle
WO 94/26498 PCT/US94/05035
smoothly so that the shaping of the inner bottle can be facilitated. Since the
inner bottle
is in contact with the outer bottle, it is possible to facilitate the cooling
of the inner
bottle by cooling only the outer bottle.
Further, since it is possible to prevent the outer and inner bottles from
fusing with
each other by cooling the outer bottle in the blow mold for a predetermined
period of
time and thus cooling the inner bottle via the outer bottle,, it is possible
for the inner
bottle to separate smoothly from the outer bottle so that the deformation of
the inner
bottle by pressure reduction can be carried out easily and reliably. If the
outer bottle is
molded with the circumferential ribs serving as the air passageways, it is
reinforced by
the circumferential ribs and hence does not deform, even when the inner bottle
is
deformed by pressure reduction. These circumferential concave ribs also
prevent
deformation of the bottle when it is gripped.
